1. Technical Field
The present invention relates to an optical system through which laser light passes and to a laser processing apparatus.
2. Description of the Related Art
With a laser processing apparatus, laser light is transmitted to a processing head from a laser oscillator via an optical fiber, and the laser light is focused by lenses in the processing head to increase the energy density of the laser light, thereby welding or cutting a workpiece. Here, the workpiece is a metal, an alloy, or the like. Examples of the laser oscillator include a CO2 laser oscillator in which CO2 is used as a medium, a YAG laser oscillator in which a crystal having a garnet structure formed of oxides of yttrium and aluminum is used as a medium, a fiber laser oscillator in which an optical fiber itself is used as a medium, and so forth.
Japanese Unexamined Patent Application, Publication No. 2006-192503 discloses an invention related to a laser cutting method, which is a technique for cutting a metal workpiece having a thickness of 5 mm or less by using a bifocal lens that focuses laser beams at two locations, thus having a focal distance between 80 mm and 135 mm.